HVAC control unit diagnostics

[Tom]

Here are diagnostic charts in a downloadable 5-page PDF format to help test the motors, solenoids, and sensors in the main HVAC flapper (heater core) box under the dash. Without testing these parts, it can be hard to know if the climate control unit itself is bad (common) or if one of the motors, sensors, or solenoids are bad (also common).

hvac diagpics pic carpokes.jpg

944 HVAC diagnostic test chart updated 102724.pdf

[Tom]

[RJB 968]

The video and check sheets are great - thanks!
My sensors all checked out and gave consistent readings. However the internal temp reads 50c....it looks like it has maxed out. The system wont produce any heat, which I assume is related to the reading on the internal temp gauge
What do I need to look for?

Thanks

[Tom]

The video and check sheets are great - thanks!
My sensors all checked out and gave consistent readings. However the internal temp reads 50c....it looks like it has maxed out. The system wont produce any heat, which I assume is related to the reading on the internal temp gauge
What do I need to look for?

Thanks

Do you mean the sensor measured at A2 reads around 3600 ohms (~50c)? If so, I'd start by checking to make sure the sensor is soldered securely to the end of the wires... If it is, and if the sensor it self reads that far off, you can save a lot of money by just soldering a new sensor into the existing sensor assembly. See post #4 in this thread for a suitable replacement sensor and some pictures to show what I mean....

https://www.carpokes.com/viewtopic.php?t=1007

[Carl944]

Footwell solenoid failure here, so very useful

[Belgian951]

This is just in time. In my last drive, I noticed that the heating system is always putting out hot air. I put all sliders to the left, airco button off, fans on, temp dial on 18. Hot air always, at any fan speed.

I still have to do clarks' diagnostics tests but this will be useful.

[Tom]

This is just in time. In my last drive, I noticed that the heating system is always putting out hot air. I put all sliders to the left, airco button off, fans on, temp dial on 18. Hot air always, at any fan speed.

I still have to do clarks' diagnostics tests but this will be useful.

When a 944 has hot air all the time, there's a 93.29% chance that the heater chip broke.

[Belgian951]

This is just in time. In my last drive, I noticed that the heating system is always putting out hot air. I put all sliders to the left, airco button off, fans on, temp dial on 18. Hot air always, at any fan speed.

I still have to do clarks' diagnostics tests but this will be useful.

When a 944 has hot air all the time, there's a 93.29% chance that the heater chip broke.

I hope this is the case for me, would be a cheap fix for once!

[Belgian951]

This is just in time. In my last drive, I noticed that the heating system is always putting out hot air. I put all sliders to the left, airco button off, fans on, temp dial on 18. Hot air always, at any fan speed.

I still have to do clarks' diagnostics tests but this will be useful.

When a 944 has hot air all the time, there's a 93.29% chance that the heater chip broke.

Sure looks like it.

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[7b944]

Hi Tom, Thanks so much for the HVAC diagnostic info and for starting CARPOKES. I've read most of the 944 posts but not had reason to post till now. My 87, 951 owned since 2004, has over the past few years, required turning the temperature knob progressively further CW to set heat and AC to a comfortable level. Now full CW does not raise AC temp, set point so am suspecting a sensor or other component aging. When I get time to pull the control unit, I intend to use your diagrams to test. Appreciate any additional suggestions if the sensors should check out ok. Thanks, Dave